People worldwide play a number of indoor and outdoor sports, games, and contests that utilize a thrown object or device, such as soccer, baseball, tennis, basketball, football, ultimate, shot put, discus, and javelin. In the sport of American football, the regulation football itself—for professional or collegiate leagues—is a pressurized air bladder weighing about four hundred twenty grams when inflated; smaller counterparts for children's leagues weigh approximately two hundred grams. These pneumatic footballs are usually made out of combinations of materials such as natural or synthetic leather (including the traditional “pigskin”), natural or synthetic rubber, and, in many cases, fabric or polyvinyl chloride laces.
These regulation footballs are designed to be rather incompressible when pressurized in order to provide a ball that can be readily clutched when caught or carried and that has appropriate spring when kicked. One downside to these footballs is that they can be quite stiff and hard when striking a person or object. The ends of the regulation football particularly, which are constructed by leather and rubber material folded in on itself, can be particularly hard and pointed.
A top-tier professional or collegiate quarterback can throw a regulation football up to seventy yards in the air. In order to extract this level of performance, the athlete must be very fit and much practiced at throwing the football.
This action of throwing the football can also be considered “launching” the football, since a football has a shape, design details, and distribution of mass sufficient to perform well as an aerodynamic device if launched within a certain set of parameters. In fact, automatic football passing machines are often used for practice and training drills for football players from children through adult (see, e.g., http://jugssports.com/productdetalaspx?id=625; http://www.livestrong.com/article/350290-football-throwers-for-kids; http://menversus.com/articles/Training-the-receivers-of-tomorrow; and U.S. Pat. Nos. 3,662,728; 4,261,319; and 5,207,421; and 6,718,961).
When launched or thrown, a football is moved in both the forward and upward directions to create a trajectory. The distance and duration of the football's flight is greatly enhanced if it is launched with the smallest possible frontal area of the ball facing the direction perpendicular to the trajectory, in order to minimize drag.
The flight of the football is further enhanced in terms of duration, accuracy, and stability if spinning is induced by the user or launching device as the ball is released (i.e., the desired, if misleadingly titled, “spiral” throw is achieved). This spinning around the longitudinal axis creates angular momentum that, in a regulation football, is stored in the mass of the bladder and its cover that define the shape of the football. This angular momentum serves to maintain the football as close as possible to the most efficient aerodynamic orientation: spinning perfectly around its longitudinal axis with as great a rate of rotation as possible. In football terms, this flight characteristic and orientation is known as a “tight spiral.” Thus, the angular momentum imparted by the user, or launching device, is critically important to ensuring the football is thrown as far as possible.
In an effort to minimize some of the safety issues described above, and further to bring football into certain indoor spaces (such as gymnasia and field houses), Parker Brothers introduced the Nerf® foam footballs that have proliferated until becoming a ubiquitous part of American culture. The prototypical foam football is a single mass of closed-cell foam weighing approximately two hundred grams. Due to its lower mass and energy absorptive nature, it is much safer in outdoor environments. However, it is not suitable for all situations because it still weighs enough to damage delicate or fragile objects.
Many of these problems that plague pneumatic and foam footballs also affect the thrown devices utilized in other activities (e.g., soccer, baseball, discus, javelin), such as those identified above.
Foam footballs are injection-molded and produce a ball of the same general shape as a regulation football. The injection-molding manufacturing technique initially produced foam footballs of nearly constant mass comprising single-density foam with a thin skin. Foam balls are significantly less likely to inflict personal injury or property damage when in use. However, foam footballs are not capable of being thrown as far as pneumatic footballs because they have less mass, because their uniform density cannot store as much angular momentum, and because of the energy-absorbing and energy-dampening characteristics of the foam.
The mass of the single-density foam ball is evenly distributed inside the entire volume of the ball, reducing the opportunity for the user to impart angular momentum via the spinning of the ball at launch. This absence of angular momentum results in a more rapid decay of the spin of the football, to levels at which the axial orientation of the ball rapidly succumbs to the force of air and enters into a tumble, which greatly increases the frontal area of the ball (and, therefore, drag), further decaying aerodynamic efficiency and cutting short the flight trajectory.
More recently, foam footballs balls have been co-molded with two or three densities of foam. For example, recent highly stylized foam footballs have a core of higher-density (heavier) foam, surrounded by lower-density (lighter) foam, and surfaces with embossed surface details. They perform more poorly than the early foam footballs due to the ineffective distribution of the majority of the mass, near the spinning axis, and the aerodynamic drag caused by the design details on the surface of the football.
The reduced performance of foam footballs may be considered by some a reasonable a trade-off for the corresponding improvement in safety, but one key trait of the pneumatic football remains. The distinct shape, and spring characteristics (large single-cell dynamically charged pneumatic spring characteristics in inflated footballs; small multi-cell dynamically charged pneumatic spring characteristics in foam footballs), of a football lead to this characteristic: when a football strikes the ground, it bounces off in a wildly variable, multi-axis trajectory. On subsequent bounces will often entirely change both direction and spin, continuing with this random, chaotic movement until the energy imparted at launch is depleted.
While this characteristic is an essential part of the game of football, it can be an inconvenience or safety hazard when footballs are used outside of designated football fields. In front yards, streets, and parks all across America, people who play catch with footballs endure this chaotic dynamic of the crazily bouncing football. Sometimes very real damage is done to individuals and property by thrown or bouncing footballs. Although of diminished amplitude in foam footballs due to the dampening effect of the foam material, this trait still results in wayward foam footballs bouncing into others' picnics and, with children in pursuit, onto busy streets.